It is unanimously accepted that the Holy Qur'an and the pure sunna are the sources of legislation and the custodians of Islamic thought and knowledge.

Imam Muhammad Baqir (a.s.), the master and authority of the jurists and one of the Imams of the Prophet's household from whom Allah removed all filth and purified with the utmost purification, summarized this belief in the following words:

"Surely Allah, Blessed and Exalted, is He Who did not leave out any matter of which the community stands in need, but He revealed it in His Book and explained it to His Apostle (s.a.w.). And He assigned a limit to everything and a proof indicating it. And He specified a punishment for whoever transgresses the limit."

The Imams of Ahl-lul-Bait (a.s.) have, indeed, enriched Islamic legislation with their expositions and elaborations of the Book and the Prophetic tradition. This exposition was a real continuation of Shari'a laws, so it is part of the sunna. The great jurist Shahid Sayyid Muhammad Baqir Sadr described this fact in these words: "Thus it becomes clear that changing the rules of the Shari'a, through abrogation, is also one of the factors that bring about conflict originating from this factor, and only affects the stipulation emanating from the Prophet (s.a.w.) not those from the Imams (a.s.).

This is so because the period of legislation ended with the close of the Prophetic era and the narrations that emanated from the Infallible Imams (a.s.) were only an elaboration on the Prophet's legislations."

Since the Book and the sunna together are the sources of Islamic legislation, the two other sources i.e., intellect and consensus (ijma') are secondary sources serving as ways to discover the legislation and not, themselves, legislators. The intellect, as a source of legislation, is defined as "an issue perceptible to the intellect while it is able to deduce a Shari'a rule from it. An example of these issues is the intellectual proposition that enjoining a thing entails enjoining its prerequisities (muqaddimat).

Consensus (ijma) has been defined by the Shi'a Imamiyya School as: "The consensus of scholars with legal opinions from among the preceding jurists of the period of occultation, on a certain ruling, while the verbal source specifying the ruling remains unknown. These jurists have met a situation that evokes a state of conviction and a settled belief which detects the existence of a legislative proof possessed by the jurists and those who preceded them."

In addition to these secondary sources mentioned above, some Islamic schools recognized sources, such as, analogy 'qiyas', discretion 'istihsan', public good 'masalih mursalah', teaching of the companions 'madhhab al-Sahbi'….etc. A lot of debate has taken place on the weight of evidence 'hujjiya' and the nature of these sources.

Both the Imamiyya school and the other Islamic schools, which subscribe to the idea that all forms of analogy are evidence, regarded the analogy in which the basis or cause 'illa' is expressed in the clear law 'Mansu al-Illa' and analogy in which the deduced law holds a prior position to that of the clear stipulation on which the analogy is based 'Qiyas al-Awlawiyya' as evidence. The only point of conflict between the two views is analogy of comparison 'qiyas al-Tamsili'; that is, to compare a part of a question to a part of another and the analogy in which the basis or cause is deduced rather than expressed in the clear stipulation.

The Holy Qur'an and the Pure Sunna contain rich and adequate legislative material. In the Qur'an alone there are hundreds of verses directly enacting laws and rules or conveying thoughts, and legislative concepts from which laws can be formulated. Thousands of Prophetic traditions serve as illucidation to those verses and legislative roles. Hundreds of these texts form the general legislative fundamentals that contribute in enriching legislation and expanding its horizons.

To illustrate, we shall review some of these verses, traditions and narrations to observe the special feature of the constituent of Islamic legislation. Allah, the Most High says:

"Surely Allah enjoins justice and the doing good (to others) and the giving to the kindred, and He forbids indecency and evil and rebellion…" Holy Qur'an (Nahl 16: 90)

"…and has not laid upon you any hardship in religion…" Holy Qur'an (Hajj (22: 788)

"…and women have rights similar to those against them in a just manner,…" Holy Qur'an (Baqara 2: 228)

"And surely We have honoured the children of Adam, and We carry them in the land and the sea, and We provide them with good things, and We have made them to excel highly most of those whom We have created." Holy Qur'an (Isra' 17: 70)

These verses of the Qur'an carrying ample legislative principles have their counterparts in the pure sunna. A large number of legislative traditions present the bases for legislative principles from which many laws can be formulated. Other traditions and Prophetic statements provide us with legislations and rules that govern individual relations, situations and positions while carrying a general sense suitable for application in identical cases.

Here, we shall mention some traditions that take the form of legislative principles:

The Holy Prophet (s.a.w.) says:

"No one shall harm nor be harmed."

"Obligation has been suspended in my ummah in respect to nine cases:Mistake, forgetfulness, what they do under duress, what they do not know, what they cannot do, what they are forced to do by circumstances, envy, evil omen, and thought over a devilish insinuation concerning creation, as long as nothing isgiven as evidence." It has been reported from him (s.a.w.) that:

"A Muslim is a brother to a Muslim, he shall not cheat him nor act treacherously towards him nor backbite him. His blood is prohibited, so is his property except by his permission ..."

"In Islam, men are equal ..."

"Men from their origin in Adam are alike and equal."

"Men are equal like the teeth of a comb."

"Allah has enjoined on the rich (to spend) what will suffice the poor, so if the poor suffer starvation Allah reserves the right to hold the rich responsible…" "Every loan to which a profit accrues is interest (riba)."

"I was not sent to amass wealth, but to spend it."

"Believers shall conduct their affairs according to their terms."

"Everything is lawful to you until you know that it is unlawful."

"There is no obedience to a creature where disobedience to Allah is involved." "The ruler is a shepherd and he is responsible for his flock." "Religion is nothing but love."

"Desire for your brother what you desire for yourself. Dislike for him what you dislike for yourself."

"Surely, your body has a right over you."

Just as the Qur'an and the Prophet's sayings constitute a source for legislation and regulating social life, his confirmation of actions he regards to be in conformity with Qur'anic legislation and his practical life and behaviour provide a wide horizon for legislative material.

These sources deal with such matters as the fitness of the legal rules, his relationship with the governors, army commanders and the community at large, his legal responsibilities, etc. This field of legislation forms the constitutional subject matter in modern legal jargon.

The narrations reaching us from the Imams of the Prophet's household, like the Qur'an and the Prophet's sayings, present copious materials for legislation. These narrations elucidate and serve as a commentary on the Qur'an and Prophetic tradition, sunna. This source material serves as foundations for legislation, addressing social problems and regulating human life with its various spheres. Islamic jurists rely on these fundamentals to deduce rules for novel conditions.

A careful study of the samples of these verses and traditions that run into hundreds of ideological and legislative texts with a fundamental and general nature, not limited by time or space, will reveal the secret behind the eternal aspect of Islamic legislation, its universality and ability to cover social evolution and development and play a leadership role in overall human existence. The law in its capacity as the source of order in human life contributes immensely in man's progress or backwardness according to the nature of the law and its world view.